Field of the Invention
The present invention relates to golf balls. Specifically, the present invention relates to improvement of dimples of golf balls.
Description of the Related Art
Golf balls have a large number of dimples on the surfaces thereof. The dimples disturb the air flow around the golf ball during flight to cause turbulent flow separation. This phenomenon is referred to as “turbulization”. Due to the turbulization, separation points of the air from the golf ball shift backwards leading to a reduction of drag. The turbulization promotes the displacement between the separation point on the upper side and the separation point on the lower side of the golf ball, which results from the backspin, thereby enhancing the lift force that acts upon the golf ball. Excellent dimples efficiently disturb the air flow. The excellent dimples produce a long flight distance.
US2005/0101412 (JP2005-137692) discloses a golf ball in which the standard deviation of the sizes of dimples is low. The standard deviation of the sizes of the dimples influences the flight performance of the golf ball. It is known to one skilled in the art that a golf ball in which the standard deviation is low has excellent flight performance.
US2007/0298908 (JP2008-389) discloses a golf ball in which the density of dimples is high. The density of the dimples influences the flight performance of the golf ball. It is known to one skilled in the art that a golf ball in which the density is high has excellent flight performance.
When small dimples are arranged in narrow zones each surrounded by a plurality of dimples, a dimple pattern that provides a high density is obtained. However, the small dimples are unlikely to contribute to turbulization. In a golf ball having such small dimples, the standard deviation of the sizes of the dimples is high. Increasing the density of the dimples and decreasing the standard deviation of the sizes of the dimples are contradictory to each other.
The greatest interest to golf players concerning golf balls is flight distance. In light of flight performance, there is room for further improvement in a dimple pattern. An object of the present invention is to provide a golf ball having excellent flight performance by achieving, at the same time, increasing the density of dimples and decreasing the standard deviation of the spherical surface areas of the dimples, which are contradictory to each other.